Amplifying system



Patented Aug. 1, 19 33 1 UNITED 4 STATES PATENT OFFICE 1 v 920,011 1 IAmmrfrmo. SYSTEM Anton Leendert lands, assignor America,

'limmer, Eindhoven, Nether.-

Radio Corporation of a Corporation of Delaware Application October 3,1929, Serial No. 396,991, and in the Netherlands October 4, 1928 6Olai'ma' (Cl. 179-171) My present invention relates to receivers, and,more particularly, to circuit arrangements for amplifying electricaloscillations.

It has been proposed to provide a circuit arrangement for amplifyingelectric oscillations by means of two thermionic devices which. are soconnected that the output circuit of the former is common to the gridcircuit of the second device, this latter device working, consequently,with a positive mean grid bias that is equal to the product of thecurrent and the resistance of the path of discharge between the grid andthe cathode of the last mentioned device.

Accordingly, in this invention an especially simple and also efllcientcontrol of the degree of amplification is assured by the grid and thecathode of the second device being connected with the interposition of avariable resistance.

Thus, indeed, the highly desirable condition is secured that on adecrease of the amplification (by reduction of the resistance) thepositive grid bias, and consequently the energy expenditure in thesecond device, falls likewise.

The novel features which I believe to be characteristic of my inventionare set forth in particularity in the appended claims, the inventionitself, however, as to both its organization and method of operationwill best be understood by reference to the following description takenin connection with the drawing in which I have indicateddiagrammatically one circuit organization whereby my invention may becarried into eifect.

35 One circuit arrangement according to the invention isdiagrammatically shown onthe accompanying drawing.

The oscillations to be amplified (for example audio frequency currents)are led into the primary of an input transformer Ti, the secondary ofwhich is connected between the grid and the cathode of a triode I. Theanode of, I is connected to the positive pole of a battery B, and thecathode of I is connected to the grid of a triode II which serves as thefinal amplifier. The anode of II is connected through the primary of anoutput transformer Tu to the positive pole of B and the cathode of II isconnectedto the negative pole of B.

In-conclusion, a variable resistance R is connected in parallel to thepath of discharge between the grid and the cathode of the valve II, andenables the degree of amplification of the 5 device to be varied withincertain limits. The output current of I is, indeed, distributed aboutthe resistance R and the path of discharge (grid cathode) of valve II sothat when R. is reduced the grid current of II, and consequently thevalue of the positive grid bias .of this valve, 'decreases. This has thedesired effect that the anode current and consequently the energyexpenditure (the anode dissipation) in the valve 11 diminishes.

While I have indicated and described a system for carrying my inventioninto effect, it will be apparent to one skilled in the art that myinvention is by no means limited to the particular organization shownand described, but that many modifications in the circuit arrangements,as well as in the apparatus employed, may be. made without departing,from the scope of my invention as set forth in the appended claims. WhatI claim is: 1. In an amplifier circuit a plurality of space dischargedevices having cathode, anode and control electrodes, a source ofpotential, the cathode of one of said devices being directly I connectedto the control electrode of a following device, means for operating saidcontrol electrode at a positive potential with respect to the cathode ofsaid last named' device, a variable impedance connected between saidcontrol elecrode and the low potential side of said source with respectto its cathode, and an impedance path connected across said grid-cathodepath.

3. In an amplification system comprising in effect a pair of thermionicdevices connected so that the output circuit of one includes thegridcathode path of the other, means for operating said latter device ata positive mean grid bias with respect to its cathode, and a resistanceconnected across said grid-cathode path.

4. In an amplificationsystem, a pair of-thermionic devices connected sothat the output circuit of one is common to-the grid-cathode circuit ofthe other, means for operating the second device .at a positive meangrid bias with respect to its cathode, and means for varying saidpositive mean grid bias for controlling the amplificationcharacteristics of the system.

5. In an amplification system in which two thermionic devices areconnected so that the effect, a pair of cascaded spacedischargeldevices,

each of said devices including anode, cathode and grid electrodes, aconnection between the grid and cathode 'of the first device includingmeans for connecting thereto a source ofenergy to be amplified, a sourceof space current for both of said devices having positive andnegative'sides, a direct connection between the anode of the first ofsaid devices and the positive side of said source, means for operatingthe second device at a positive mean grid bias potential with respecttoits cathode comprising a direct connection between the cathode of thefirst device and the grid electrode 01. the second device, and aconnection from the cathode of the second device to the negative side ofthe source whereby the grid cathode path of the second device is, ineffect, included in the output circuit of the first device, an impedancepath shunted across the grid-cathode path of said second device, and' aload coupling impedance connected between the anode of the second deviceand the of said source.

ANTON LEENDERT TIMMER.

positive side

